1. Field of the Invention
The present invention relates generally to fuel dispensing equipment located at vehicle refueling stations, and, more specifically, to a leak detection system using compressed air to selectively pressurize the vapor recovery portion and fuel dispensing portion of a fuel dispenser to evaluate the equipment for leakage problems.
2. Description of the Related Art
Refueling stations employ a fuel dispenser typically provided in the form of a nozzle-based assembly having a flexible fluid-conveying hose with a discharge nozzle at one end that the operator manually activates to control the dispensing of fuel. Integrated with the fuel dispenser is a vapor recovery system that typically uses a vacuum-assist pump apparatus to facilitate the collection of vapor effluents that are displaced from the vehicle tank reservoir as liquid fuel is introduced into the tank. It is clear in terms of human safety and environmental protection that both the vapor recovery and fuel dispensing portions remain structurally intact to protect against unwanted fluid loss or vapor release into the atmosphere arising from material or structural failures in the equipment. The need to sustain a proper level of equipment integrity extends not only to components such as seals that function specifically to provide a closed system with respect to the fuel and vapor pathways, but extends as well to every other component that interacts with or assists in the communication of liquid fuel and recovered vapors. A need therefore exists to provide a diagnostic apparatus that examines the fuel dispensing equipment and enables the testing operator to determine the origin and extent of any weakness in the equipment that would allow either fuel or vapor to escape.
One conventional approach to identifying leakage problems involves measuring the flow rate of the liquid fuel supplied by the fuel pump needed to maintain the pressurization of the fuel line within a certain range. The leak test performed in accordance with this approach is conducted during normal operation of the fuel delivery system. Another approach involves isolating a segment of the fuel delivery pipeline and determining whether leakage has occurred by measuring any pressure changes in the liquid fuel contained in the isolated pipeline segment. Yet another conventional leak detector utilizes a test reservoir filled with fuel and which is disposed in fluid communication with the fuel line. Monitoring pressure and temperature changes in the test reservoir provides data indicative of the leak rate of the fuel line.
These conventional apparatus attempt to identify leaks in the fuel delivery system by analyzing the in-line liquid fuel for changes in characteristic parameters such as pressure and temperature. This form of analysis typically requires activation of the fuel delivery system, particularly the fuel pump, so that the fuel line can be pressurized and thereby readied for the diagnostic leak test. Performing a leak detection test on in-service fuel dispensing equipment, however, presents the obvious drawback that fuel is still permitted to escape even though the leak may be successfully detected. Other conventional test apparatus operate on the fuel delivery system when it is inactivated, although such apparatus are still characterized by the need to pressurize the fuel line under investigation through simulation or by utilizing a test reservoir. What is therefore needed is a diagnostic method and apparatus that allows the fuel delivery system to be probed for leaks during an inactivation period and that does not require the fuel line to be pressurized with fuel in order for the leak test to be conducted.